Average temperature control mech



March 23, 1937. E. A. TAYLOR ET A1. Re 20,310

AVERAGE TEMPERATURE CONTROL MECHANISM FOR HEATING SYSTEMS Original FiledJan. 8, 1932 3 Sheets-Sheet l ...UWE

March 23, 1937. E. A. TAYLOR ET AL Re- 20,310

AVERAGE TEMPERATURE CONTROL MECHANISM FOR HEATING SYSTEMS Original FiledJan. 8, 1952 3 Slmets-Sheerl 2 ons Jen figg/lar Pezzo@ Q5/in A zma/m f 2March 23, 1937. E. A. TAYLOR sr AL Re. 20,310

AVERAGE TEMPERATURE CONTROL MECHANISM FOR HEATING SYSTEMS Original FiledJan. 8, 1952 3 Sheets-Sheet 3 S SN r s 4m/W W m g e 1a n fm @a m W IA mm f E @NNN M I f a NNN S www NNN @i nib k. www wm N i Wmv l SK@ h .WQQ

Reissued Mar. 23, 1937 AVERAGE TEMPERATURE CONTROL MECH- ANISM FOR.HEATING SYSTEMS Elbert A. Taylor, Arlington Heights, lll., Millard D.Pence, New York, N. Y., and Clayton A. Dunham, Glencoe, lll., assignorsto C. A. Dunham Company, Marshalltown, Iowa, a corporation of IowaOriginal No. 1,921,172, dated August 8, 1933,

Serial No. 585,530, January 8, 1932. Application for reissue February21, 1935, Serial No.

l1 Claims.

This invention relates to a new and improved average temperature controlmechanism for heating systems and more particularly to an improvedthermostatically controlled apparatus by means of which the supply ofsteam to a steam heating system is automatically controlled inproportion to variations from a predetermined temperature, thecontrolling temperature at any instant being the average of thetemperatures then existing l'.) at a plurality of different locations,that is to say three or more locations, in the space heated by thesystem.

More specifically, the heating system which is preferably of thesub-atmospheric type provided t3 with a differential pressure control ofthe steam supply to the radiators, is also provided with anelectrically-operated motor control of the supply valve whereby theopening of the valve is controlled in proportion to the variations froma` 0 certain predetermined temperature. This controlling temperature isdetermined by a plurality of separate thermostats positioned in various1ocations in the space to be heated. By plurality of thermostats, as theterm is used herein, is in- `tended three or more. In some installationsheretofore known involving the use of a plurality 0f separatethermostats, the connections have been such that each thermostatseparately controlled the steam supply valve, so that each one of thethermostats would have to be separately satised before the valve couldbe automatically adjusted. In other words, the desired minimum ormaximum temperature would have to be attained at the location of eachone of the thermostats. In

another known arrangement, involving a proportionate control of thevalve, the thermostats have been connected in parallel with theintention of controlling the valve in response to the average of thetemperatures registered by the several different thermostats. Thislatter arrangement has proved ineffective where three thermostats areconnected in parallel due to the fact that when two of the thermostatsare subject to extreme temperatures in opposite directions, theapparatus will respond to a fixed intermediate temperature regardless ofthe operative position of the third thermostat. Similar results areobtained when more than three thermostats are used.

According to the present invention, the plurality of separatethermostats are connected in series, the variable resistances controlledby the thermostats being modified in a manner to permit this seriesconnection, all as hereinafter ex- 55 plained in detail. As a result thesteam control valve will be regulated ln response to the average of theseveral temperatures to which the different thermostats are subjected,regardless of the positions of any one or more of these thermostats.

'I'he principal object of this invention is to provide an improvedaverage temperature controlling mechanism for heating systems, such asbriey referred to hereinabove and disclosed more in detail in thespecifications which follow.

Another object is to provide an improved form of thermostatic controlmechanism for a heating system.

Another object is to provide an improved system of connectingthermostatically controlled mechanisms in series so that the effectivecontrolling temperature will be an average of the temperaturesregistered by the several thermostats of the series.

Other objects and advantages of this invention will be more apparentfrom the following detailed description of one approved form ofapparatus constructed and operating according to the principles of thisinvention.

In the accompanying drawings:

Fig. l is a diagrammatic elevation of a steam heating system with theimproved controlling mechanism applied thereto.

Fig. 2 is a central vertical section through the reducing valve,partially broken away.

Fig. 3 is a partial side elevation of the valvecontrolling mechanism,looking from the right at the lower portion of the apparatus shown inFig. 2.

Fig. 4 is a wiring diagram for the thermostatic andelectrical-controlling apparatus.

Fig. 5 is a wiring diagram, corresponding to the left-hand portion olFig. 4, showing an old or known form of control mechanism, anddisadvantages of which are eliminated by the lmproved construction shownin Fig. 4.

Reference will rst be made to Fig. 1 which shows a heating system of thetype with which the improved controlling mechanism is best adapted tocooperate, although this improved controlling mechanism may be used withothertypes of heating systems as will be hereinafter apparent. Theheating system here shown is of the sub-atmospheric steam heating typedisclosed in the patent to Clayton A. Dunham 1,644,114, granted October4, 1927, and in the copending application of David N. Crosthwait, Jr.,Serial No.

425,681, filed February 3, 1930. This heating system comprises a boileror generator A from which the steam flows through supply main B and theimproved flow control valve C into the portion B' of the supply mainfrom which the radiators D are supplied. At the outlets of the radiatorsare steam traps E, F is the return main, G is an accumulator tank forthe condensate, the exhausting mechanism is indicated generally at H,and J is the differential pressure controller for the exhaustingmechanism. At K is indicated generally an electric controlling mechanismfor the valve C, this mechanism K being under the control of apluralityof separate thermostatic devices indicated at L, L' and L". The presentinvention is concerned particularly with improvements in the mechanism Kand the thermostats L, in combination with the elements with which theseparts cooperate.

The controlled seam in main B' passes through risers I and inlet valves2 into the respective radiators D. Suitable orice plates, such asdisclosed in the Dunham patent hereinabove referred to, may beinterposed in the respective risers I, preferably between the inletvalves 2 and the radlators for proportioning the steam ilows to therespective radiators in accordance with the size or` condensing capacitythereof. The steam traps E are adapted to close when the radiators arelled with steam and prevent the escape of steam therefrom. Whencondensate and non-condensable gases accumulate in the radiators, thetraps E will open and permit the condensate and noncondensable gases toflow out or to be drawn out by the lower pressure maintained in thereturn side of the heating system. These gases and the condensate flowthrough pipes 3 into return main F and thence through the strainer 4into the aci' cumulator tank G. In a similar manner, the condensate andgases accumulating in the portion B of the supply main pass out throughoat and thermostatlc trap 5 into return main F and thence into theaccumulator tank G. The exhausting mechanism H comprises a separatortank G and a pump 1, driven by motor 3, to withdraw water from the lowerportion of tank 5 and force it through ejector 9 and thence back intothe upper part of tank 6 together with the gases and condensate whichare withdrawn from accumulator tank G through pipe Ill and check-valveII into the exhauster casing. The gases are vented from separating tank6 through pipe I2 provided with outwardly opening check-valve I3. When acertain amount of liquid has accumulated in tank 6, a oat-controlledmechanism, indicated generally at I4, operates to open a normally closedvalve I5 so that the pump 1 can force a part of the liquid out throughpipe I6 provided with checkvalve i1, and thence through pipes I8 and I3into the boiler.

The exhausting mechanism H is operated whenever it is necessary to buildup the pressure differential between the ,supply and discharge sides ofthe heating system, or whenever it is necessary to transfer accumulatedcondensate from the accumulator tank G into the separating tank 6. Thecontrol mechanism J comprises a differential-pressure controller 2liwhich automatically opens and closes a switch 2| which operates throughstarter 22 to control the motor 8. The differential pressure controllercomprises a diaphragm subjected on its opposite sides to the pressuresexisting in the supply and return sides of the heating system. For thispurpose control pipes 23 and 24 extend to surge tanks 25 and 25positioned in the horizontal section 21 of an equalizing pipe extendingbetween the supply and return sides of the heating system, in theexample here shown the relatively high pressure end of pipe 21communicating through pipe 23 with the supply main B', and therelatively low pressure end communicating through pipe 29 with thereturn main F. A check-valve 30 is positioned in the equalizing pipe 21between the relatively high pressure surge chamber 2S and the relativelylow pressure surge chamber 25. This valve opens toward the high pressureside of the system andwill normally remain ciosed unless for some reasona lower pressure temporarily exists in the supply main than the pressurein the return main, whereupon valve 35 will open to equalize thepressures. This control mechanism J will operate. in a well knownmanner, to cause the exhausting mechanism to function whenever thepressure differential between the supply and discharge sides of theheating system falls below a predetermined minimum, and to throw theexhausting mechanism out of operation whenever the desired pressuredifferential has again been established. Also, a float-controlledmechanism in the accumulator tank G (disclosed in detail in the Dunhampatent referred to above) acts through switch mechanism 3l to start theoperation of exhausting mechanism H whenever a predetermined amount ofcondensate has accumulated in the tank G.

The improved control valve C will now be described, referring to Figs. 2and 3 in addition to Fig. l. This valve comprises a casing 32 having aninternal web 33 separating the supply chamber 34 from the relatively lowpressure chamber 35. The supply chamber 34 is connected with the supplymain B leading from the boiler, and relatively low `pressure chamber 35connects with the portion of the supply main B' from which the radiatorsare supplied with low pressure steam. The web 33 is formed with thealigned valve seats 36 and 31, with which cooperate respectively theconnected and substantially balanced valves 38 and 39. Each of thevalves 38 and 39 is preferably of the sleeve type here shown, with theslots `or openings 39' in the sleeve walls so designed that the totalarea of the valve opening will increase by equal lncrements as the valveis moved upwardly. A removable closure plate 40 permits access to theupper portion of the casing 32. A closure plate 4I covers the opening inthe lower portion oi casing 32, this closure plate having an. outwardlyprojecting flange 42 secured to the casing by bolts 43, and an upwardlyprojecting flange 44 to center the plate 4I properly within the openingin the lower portion of the casing. This closure plate 4I is formedintegrally with an upward extension 45 of the diaphragm casing member46. This upper dished diaphragm casing member 46 ls formed at its loweredge with an outwardly extending flange 41, and a similar lowerdiaphragm casing member 4B is formed on its upper edge with an outwardlyextending flange 48. The two casing members 48 and 43 are clampedtogether at opposite sides of an enclosed flexible diaphragm 50 by meansof a plurality of bolts 5D' passing through the flanges 41 and 43 andthe peripheral portion of diaphragm 50. The chamber 5I within lowercasing member 43 is open to the atmosphere through central passage 52.The chamber 53 above the diaphragm 5|) is connected through intermediatechamber 54 with an upper chamber 55 from which leads a pipe 55 whichleads to a surge chamber 51 communieating through pipe 58 with thesupply main B', The chambers 53, 54 and 55 are all at substantially thesame pressure, but the intermediate webs or baiiles 59 are designed toprevent the formation of convection currents in the liquid thataccumulates above the diaphragm and thus prevent undue heating of thediaphragm 59 from the steam passing through casing 32. The upper portion6U of a lower diaphragm casing is supported from the lower portion 68 ofthe upper diaphragm casing by means of a plurality of struts 6I. Thelower member 62 of this lower diaphragm casing is clamped to the casingmem- 10 ber 60 by means of a plurality of bolts 53 so as to enclose asecond flexible diaphragm 64 similar to the iirst described diaphragm50. The chamber 65 above diaphragm G4 is open to the atmosphere throughcentral passage 66. The lower diaphragm chamber 61 is connected throughpipe 68 with a surge chamber 69 connected through pipe I0 with returnmain F. The surge chambers 5l and 69 may be conveniently positionedadjacent one another and connected by the supporting member 1, althoughthere is no fluid connection between these two chambers.

Referring now again to Figs. 2 and 3, the upper end of a valve stern 12is threaded in valve structure 13 and provided with a lock nut 14. Thevalve stem 12 is slidable through a guide bearing 'l5 in the closureplate ll and also passes vertically downward through central passages inthe webs 59. The lower threaded portion 16 of stem 12 passes throughdiaphragm 59 and is sealed thereto by means of the diaphragm plates 'Iland 18 held in place by nuts 19 and 9|). The outer edges of thediaphragm plates are preferably Curved, as indicated at 9|, to preventany cutting action on the diaphragm as it is flexed. The lower end ofthe stern is screwed into the yoke 82 and locked in place by nut 83. Alower valve stem 84 is similarly threaded into the lower side of yoke 82and locked in place by nut B5. This valve stem B4 is sealed into thelower diaphragm B4 by means of diaphragm plates B6 and 81, held in placeby nuts 88 and 89, in the same manner as the upper valve stem isattached to the upper diaphragm.

A lever 9i) is intermediately pivoted at 9| to the lower end of afulcrum link 92 suspended from lug 93 on the lower diaphragm casingmember 48. One end of lever 99 is pivoted at 94 Within the yoke 82. Theother arm of lever 90 carries a weight 95 carried by stem 96 and yoke 91adapted to rest in any one of a plurality of notches 98 spacedlengthwise of the longer arm of lever SD. It will be apparent that byadjusting the weight 95 outwardly on the lever arm 9|), the upwardpressure exerted on the movable valve assembly will be increased.

A stop screw 40' mounted in the bottom of closure plate 40 limits theupward movement of valve assembly 13.

It will be noted that opposed Sides of the two connected diaphragms 50and El are exposed to atmospheric pressure, but the upper side of theupper diaphragm 59 is subject to the pressure in the supply side of theheating system, whereas the lower side of lower diaphragm 64 is subject1:5 to the pressure in the return side of the heating system. Therefore,the net force tending to move the valve assembly downwardly to close thevalve is always equal to the pressure differential between the supplyand return sides of the system. it will now be apparent that when thisdownward force exerted by the pressure diierential -iust equals theupward force exerted by the adjustable weight 95, the valves will be ina state of rest or equilibrium. If the pressure differential increasesabove this xed normal there will be a tendency to overcome the eiect ofweight and close the valves. On the other hand, if the pressuredifferential decreases, the weight 95 will overcome the uid pressure andopen the valves.

In case the valves 38 and 39 are absolutely balanced, that is of equalsize, the device will operate as above described. In case a semibalancedvalve assembly is used, the varying pressure eilect may be compensatedfor by employing larger diaphragm plates on one of the diaphragme thanthe diaphragm plates used on the other diaphragm. This will change theeiective area of the flexible diaphragms and compensate for theunbalanced areas of the two valves. The unbalanced pressure due to thedifference in elevation between the two diaphragms 50 and 6I may becompensated ior by a proper variation in the relative size of diaphragmplates l1, I8 and 86, 91.

In the general operation of the heating system as thus far described,the desired steam pressure in the boiler A and supply pipe B is obtainedby proper control of the res beneath the boiler A, or by the dampers orother heat controlling mechanism with which the generator is supplied.The weight 95 is set to respond to a predetermined pressure diierentialbetween the supply and return sides of the system, and the differentialcontroller J will be regulated to maintain substantially the same or asomewhat smaller pressure differential. Assuming that the temperature inthe building is below that at which the thermostats L (hereinafterdescribed) operate to close the valve C, and that the system is not yetfilled with steam, the weight 95 will operate to open the valves 39 and39 and permit a free iiow of steam through the valve C. The exhaustingmechanism H will now be in operation to lower the pressure in the returnmain, and this exhausting action will extend throughout the system sincethe traps E are now open. The traps will remain open until the radiatorsD are filled with steam, and during this time the exhausting mechanismwill be unable to establish any material pressure diilerential betweenthe supply and return mains. When the steam fills the radiators D andreaches the traps E, the traps will automatically close, after which theexhausting mechanism H will be able to establish a lower pressure in thereturn main F than exists in the supply main B'. As this pressuredifferential reaches the predetermined value it will act on thediaphragms 50 and BI to overcome the effect of weight 95 and tend toclose the valves 3B and 39 thus throttling the ow of steam to theradiators. As the operation of the valve is gradual, the valve inclosing will reach a position where the rate of steam supply to theradiators is approximately equal to the rate of steam consumption orcondensation in the radiators, so that the differential will remainsubstantially constant and the valve will tend to remain in a state ofrest or equilibrium in that position for feeding steam to the system atthe rate at which it is required. If, for any reason, the rate of steamsupply should exceed the desired rate of heat emission from theradiators, or` that rate at which the radiators will condense steam tocompensate for the heat loss from the building. the pressuredifferential will increase and the valve C will tend to close. Thecondensing rate of the radiators will then exceed the rate at whichsteam is being supplied and the supply pressure will drop so that thedifferential will diminish and CTI the valve C will tend to open againunder the influence of weight 95. It will be apparent that any increasein the pressure diierential will tend to cause the valve to close andany decrease in the differential will tend to cause it to open, and thatthe gradual action of the valve in opening and closing between itsextreme limits of travel will permit it to reach a position ofsubstantiai equilibrium that maintains the steam supply substantiallyequal to the condensing rate.

It will now be evident that in view of the fact that the valve C willact to maintain the proper differential at all times and that this canonly be accomplished when steam is filling the system at the rate thatthe system is condensing it, the valve C will act to maintain varyingsteam pressures in the radiating system in accordance with outsidetemperatures. This will result in the heat emission from the radiatorsremaining substantially equal to the heat loss from the building.

It is to be noted that in the construction of the improved control valveC no stuffing boxes are required. One side of each of the movablediaphragms 50 and B4 is exposed to the atmosphere, whereas the pressurechambers at the other sides of the respective diaphragms will becomefilled with liquid so as to prevent the direct contact of steam with thediaphragms, thus effectively sealing the system against the loss offluid pressure and prolonging the life of the dlaphragms by protectingthem from the direct action of the gases in the system.

The construction and operation thus far described is substantially thesame as that disclosed and claimed in the copending application of DavidN. Crosthwait, Jr., Serial No. 425,681, filed February 3, 1930.

In addition to the differential pressure controlling mechanismhereinabove described, thermostatic means is provided for automaticallyclosing the valve or limiting its opening movement in accordance withvariations from a predetermined average temperature to be maintainedthroughout the building that is being heated. A plurality of thermostatsL, L', L", etc. are so constructed and coupled together that the averagetemperatures registered at any instant by the several thermostats willbe the temperature which is effective to automatically control the valveC. A motor mechanism indicated generally at K (Fig. 1) is adapted tomove an amount proportionate to the variation of this averagetemupwardly independently of the yoke 32.

perature registered by the several thermostats from a predeterminedstandard temperature, and thus move or limit the movement of valve C aproportionate amount so as to effect a. proper control of the steamsupply. The present invention is concerned particularly with an improvedconstruction of the thermostatically operated mechanism whereby theaverage of the temperatures registered by the several thermostats willalways be effective to control the position of valve C.

Referring again to Figs. 1, 2 and 3, an operating lever 99 isintermediately pivoted at |00 between brackets |0| projecting downwardlyfrom the upper diaphragm casing I8. The inner end |02 of the lever isadapted to engage a portion of yoke 82 so that downward movement of thisinner arm of lever 39 will positively pull valve stem 'I2 downwardly toclose the valves 33 and 39. However, the inner arm of lever 39 can swingIn this manner the lever 39 is operable to close the valves or to limitthe amount of their opening movements, but the actual opening movementof the valves is under the control of the pressure operated mechanismpreviously described. A yoke |03 formed at the outer end of lever 39 ispivoted at |04 to a slide block |05 mounted on the operating stem |06. Acompression spring |01 surrounds the stem |06 and is confined betweenblock |05 and an adjustable nut |08. At |09 is a stop nut adjustablymounted on the upper end of stem |06 to limit the upward movement ofblock |05. At l0 is indicated a small motor assembly which is supportedby a bracket iii projecting from the lower portion of the valveassembly. A rotary operating shaft ||2 projecting from the motor casing||0 carries at its outer end a crank arm H3 to which the lower end ofoperating stem |06 is pivotally connected at Ill, Operating means areprovided within the casing l l0 whereby crank arm |3 will be rotatedintermittently, in one direction or the other, an amount proportionateto the variation from a certain predetermined temperature as registeredby the thermostats positioned at suitable locations throughout thebuilding. This movement will be transmitted through stem |06 and spring|01 to the operating lever 99, which will impart a corresponding closingmovement to the valves 38 and 39, or will so position the inner end |02of lever 99 as to limit or restrict the possible opening movement ofthese valves.

Referring now more particularly to Fig. 4, the construction andoperation of the electrically operated mechanisms L and K will bebriefly described. All of the mechanism indicated in the right-handportion of Fig. 4 may be positioned in or adjacent the casing ||0 shownin Figs. l, 2 and 3 and is connected by the three-wire circuit H5, ||6and with the thermostats L, L' and L". The main power lines |||l and H9lead through cut-out switch 20 to the motor assembly K.

At |2I and |22 are indicated the fields oi' two small electric motorswhose armatures |23 and |24 respectively are mounted on shaft |25carrying the worm |26 which drives the worm wheel |21 which is mountedon or geared to the crank shaft ||2 (see Fig. 3) which moves the valveoperating lever 99. One motor |23 rotates in one direction, and theother motor |26 operates in the other direction. The actuationg circuitsfor the motors |23 and |24 include a pair of limit switches |28 and |29,and a reversing switch |30, which elements will be described more indetail hereinafter. 'I'he actuating circuit for motor |23 extends frommain lead IIB through wire |3|, field |2|, wire |32, limit switch|23,'wire |33, relatively fixed contact |3I and movable contact |35 ofthe reversing switch |30, and wire |35 to the other main H3. In asimilar manner the actuating circuit for motor |24 extends from main IIBthrough wire |3i, field |22, wire |31, limit switch |29, wire |33, fixedcontact |39 and movable contact IIB of the reversing switch |30, andthence through Wire |36 to the other main I9.

The primary MI of a transformer is connected between the mains IIB andH9, and the secondary |42 of this transformer is connected through Wires|43 and I with the circuit wires |45 and H6 which are connected at |31and |43 respectively with the two outside wires and H6 of the three-wirecircuit leading to the thermostats. The inner ends oi the wires 6 and||1 are connected to the ends, and the middle wire ||5 is connected tothe center of a solenoid |43 having a core |50 connected through stem|5| with the movable contact member |52 of a control switch indicatedgenerally at |53. The elements of switch |53 are mounted on a carriageor plate |54 which ls pivoted at its lower end to swing about the axis|55. The Switch comprises a pair of contacts |56 and |51 in the form ofadjustable screws between which moves the contact member |52 so as toalternatively make contact with either of the relatively fixed contacts|56 and |51. The bracket plate |50 carried by switch assembly |53 isformed with a. slot |59 in which engages the pin |60. Pin |60 is carriedby a block |6| adjustable along a screw |62 carried 15 by the eccentricdisk |63 xed on the axis of worm wheel |21 so as to rotate therewith. Bymeans of screw |62 the pin |60 may be adjusted toward or from the axisof disk |63 so as to vary the angular distance that bracket |59 andswitch assembly |53 will be swung about the axis |55 as the disk |63 isrotate'd.

At |64 is indicated a balanced relay in the form of a solenoid having acore |65 connected by stem |66 with a plate |61 engaging between themovable contacts |35 and |40 of reversing switch |30 so as to move thesecontact members alternatively into engagement with the relatively xedcontacts |34 and |39. The wire |45, hereinabove referred to, extends tothe contact member |51 of switch |53, and the other wire |46 of thiscircuit extends to the contact member |56. Branch wires |68 and |69 leadfrom the circuit wires |45 and |46 respectively to the two ends of thesolenoid coil of relay |64. The wire |10 connects the central portion ofthis solenoid to the movable contact member |52 of switch |53. Whenmovable contact |52 is moved into engagement with relatively iixedcontact |56 (in the manner hereinafter described) an actuating circuitwill be completed through the left-hand half of the solenoid coil |64 asfollows: From transformersecondary |42 through wire |44, wire |45, wire|66, coil |64, wire |10, contact |52, contact |56, and wires |46 and |43back to the transformer. This will pull the core |65 to the left therebymoving contact |40 of switch |30 into engagement with contact |39 andcompleting the actuating circuit for motor |24. In a similar manner,when movable contact |52 is moved into engagement with contact |51 acircuit will be completed from transformer secondary |42 as follows:Through wires |44, |45, contact |51, contact |52, wire |10, right-handhalf of solenoid coil |64, wire |69, and wires |46 and |43 back to thetransformer. This will move the core |65 to the right and move contact|35 of switch |30 into engagement with contact |34, thus completing theactuating circuit for motor |23.

We will refer now to the simple form of thermostat indicateddiagrammatically at T in Fig. 5. This comprises a coiled thermostaticmember |1| of well known type, fixed at one end |12 and having a movableend |13 which swings to the right as the temperature rises and swings tothe left as the temperature is lowered. This movable end |13 of thethermostatic member is connected through link |14 with a contact member|15 which is in constant engagement with a resistance |16 and movablebetween the ends thereof. Assuming for the moment that one of thesethermostats such as T is connected with the controlling mechanism Kthrough the three-wire circuit H5, ||6 and ||1, instead of the series o!thermostats L, L' and L" in Fig. 4,

',-5 the wires ||6 and ||1 will be connected with the respective ends ofresistance |16 and the middle wire ||5 will extend to the movablecontact |15.

Assuming that the predetermined temperature for which the mechanism isadjusted exists at the location of thermostat T, the parts will be inthe position shown in Fig. 5 with movable contact |15 at the center ofresistance |16. It will be noted that a circuit is complete throughtransformer secondary |42 and the balanced solenoid |49 and resistance|16, which circuit comprises two parallel halves each including one-halfof solenoid coil |49 and one of the sections into which resistance |16is divided by the movable contact member |15. For example, current flowsfrom transformer |42 through wire |43, Wire |46, wire H6, portion |16'of resistance |16, contact |15, wire ||5. right-hand half of solenoid|49, wire ||1, Wire |45, and wire |44 back to the transformer. A similarcircuit is completed through the other portion |16" of resistance |16and the left-hand half of solenoid |49. When the two halves |16 and |16"of the resistance |16 are equal, as shown in Fig. 5, the current owingthrough each half of solenoid |49 will be equal and this solenoid willbe balanced so as to hold the core |50 in a central position, with themovable switch contact |52 positioned centrally between and out ofcontact with the two switch contacts |56 and |51.

Resistances |11 and |16 are positioned in the two thermostat circuits todecrease the current which constantly iiows through these circuits.

Assuming now that the temperature at the location of thermostat T risesabove the predetermined temperature for which the mechanism is adjusted,the thermostat I`|| will expand and move the contact member |15 towardthe righthand end of resistance |16 a distance which is proportionate tothe variation from the predetermined temperature. The relative strengthsof the two resistance sections |16' and |16" will be varied in the sameproportion, as will be the strengths of the currents flowing through thetwo halves of solenoid |49. In the present example, the strength of thecurrent in the left-hand half of solenoid |49 will be increased, so asto move the core |50 to the left and swing movable contact |52 of switch|53 into engagement with the relatively xed contact |56. The arcuatedistance through which movable contact |52 is swung will beproportionate to the variation from the predetermined standardtemperature at thermostat T. The engagement of contact |52 with contact|56 will `complete a circuit through the left-hand half of relay |64thus moving contact |40 of switch |30 into engagement with contact |39and completing the actuating circuit for motor |24. This motor will nowrotate the worm |26 and worm wheel |21 causing a movement'of shaft ||2and crank arm ||3 in such a direction as to lower the left-hand end oflever 99 (Fig. 2) and partially close the valves 36 and 39, or limit thepossible opening movement of these valves in case the valves havealready been closed by the pressureoperated mechanism. At the same timethe eccentric disk |63 will be rotated slowly in acounterclockwisedirection, this movement causing pin |60 which engages in slot |59 toswing the switch assembly |54 to the left until contact |56 isdisengaged from contact |52, thus breaking the circuit through relay |64and stopping the motor |24. The arcuate extent of this swinging movementof switch bracket |54, and consequently the time during which motor |24will operate and the distance through which the valves will be movedwill depend upon the arcuate distance through which contact member |52has been moved by means oi the balanced solenoid |43 which in turn isproportionate to the variation in temperature from the desired standard.It will thus be seen that the valves 33 and 33 will be closed an amountproportionate to the temperature variation above the desired standardtemperature. In an exactly analogous manner, in case the temperaturefalls below the desired standard, contact |15 will be moved to the leftthus causing movable switch member |52 to be moved against relativelyxed switch member |51, thus causing relay |34 to close the circuitthrough contacts |35 and |34 whereby motor |23 will be energized torotate the valve operating mechanism in the opposite direction and openthe valves, or rather permit them to be opened by the operation of thepressure-diaphragms. In this case the eccentric disk |33 will be rotatedin a clockwise direction so as to swing the switch bracket |54 to theright until contact |53 is disengaged from movable contact |32.

By adjusting the pin |63 radially oi' disk |63 (by means of screw |32)the distance through which the valves will be moved in proportion to anytemperature variation can be adjusted. In case pin |33 is positionedsubstantially coaxial with disk |33, it will be noted that no swingingmovement oi switch assembly |53 will result from the rotation of theeccentric disk. In such case the motor |23 or |24, as the case may be,would continue to rotate indefinitely, or until the movable contactmember |52 is returned to its central position. For this reason thelimit switches |23 and |23 are provided. When the mechanism hascontinued in operation long enough to entirely open or entirely closethe valves, one of the arms |13 or |33 ixed to disk |33 will engage theinner arm I3| of the limit switch |23 or |23 as the case may be, thusopening this switch and stopping the motor. In the example here shown,each oi these limit switches comprises a fixed contact |32 and a movablecontact |33 carried by one arm |34 of a switch lever pivoted centrallyat |35. When the arm |19 or |33 engages the inner arm |3| of the switchlever, the movable contact |33 will be swung out oi' engagement withfixed contact |32 so as to break the circuit. When the pressure isremoved from arm |3|, the contact |33 swings back into engagement withi'lxed contact |32.

In the operation as thus far described, only a single thermostat T isused to control the operation oi the valve adjusting mechanism. Itisoften desirable to control the heating system in accordance with theaverage oi' the temperatures existing at a plurality of locations in thebuilding. A single thermostat may be subject to sudden and abnormalchanges in temperature, resulting from an open window or door forexample, and i! the heating system were entirely under the control ofthis single thermostat, the heating system might be controlled in amanner unsuitable for other portions oi.' the building. By locating aplurality oi' thermostats at different selected positions in thebuilding, and controlling the heating system in accordance with theaverage of the temperatures existing at any one time at these severallocations, the system will be more economically operated and a moreconstant and dependable temperature condition maintained throughout thebuilding. In an endeavor to achieve this desired result, a plurality ofthe thermostat mechanisms of the type indicated at T have been hooked upas indicated at T, T and T" in Fig. 5. It will be noted that with such ahook-up, the left-hand portions of the several resistances |16 will beconnected in parallel in one of the thermostat circuits, and theright-hand portions will be connected in parallel in the otherthermostat circuit. As long as the variations from the standardtemperature are small at each of the thermostats, this apparatus willfunction to control the heating system approximately in accordance withthe average of the temperatures at the three thermostats. However, incase the temperature at one thermostat (such as T) falls so that themovable contact |15 is moved substantially to the left-hand end of theresistance |13, and in case another thermostat (for example T")responded to an excessive temperature such as to move the movablecontact to the other end of its resistance, the effective resistances ineach of the thermostat circuits will be reduced to a minimum so thatsolenoid |49 will be balanced and movable switch member |52 held in itscentral inoperative position. 'I'his condition of the parts will persistno matter what the position of the third thermostat may be. or, in casemore than three thermostats are so connected, all of the additionalthermostats will be ineffective to control the heating system solong asany two of the thermostats are subject to extreme temperature variationsin opposite directions.

In order to avoid this failure of the mechanism shown in Fig. to operateunder certain conditions which are often met with in the actualoperation of the heating system, the improved thermostat constructionand thermostat assembly indicated at the left of Fig. 4 have beenprovided. Each of the similar thermostatic mechanisms L, L' and L" isprovided with a pair of separate resistances |36 and |31 similar to thesingle resistance |13 used in thermostat T. Movable contact members |33and |33 engage the respective reslstances |36 and |31 and aresimultaneously adjusted lengthwise of these resistances by the movementsof thermostatic member |1| in exactly the same manner as hereinbeforedescribed in connection with the thermostat T. When a plurality ofthermostats are used, as shown in Fig. 4, for obtaining the true averageeilect which is the object of this invention, the central wire ||5 isconnected to the movable contacts |33 and |33 of the thermostat L at oneend oi the series, and the outside wires H3 and ||1 are connected to theopposite ends of the respective resistances |36 and |31 of thethermostat L at the opposite end oi' the series. The lett-hand end oi.'resistance |33 of the first thermostat L is connected by wire |33 withthe movable contact |33 engaging the similar resistance |36 of thesecond thermostat L. The right-hand end of resistance |31 oi' thermostatL is connected by wire |3| with the movable contact member |33 engagingthe resistance |31 of the second thermostat L'. In a similar manner, thereslstances of the second thermostat L' are connected with the movablecontact members of the third thermostat L and so on throughout theseries in case more than three thermostats are used. It will now be seenthat in this apparatus the effective portions oi the several resistances|33 are all connected in series in one of the thermostat circuits (thatis the circuit between wires ||5 and H3), and the effective portions ofthe other resistances |31 are all connected in series in the otherthermostat circuit between wires ||5 and ||1. With such a lconstruction, in case two of the thermostats are subject to extreme highand low temperatures.

respectively, and the movable contact members I 88 or |89 are moved toextreme positions so as to entirely eliminate in each case one of theresistances |86 or |81 from the circuits, the mechanism will not berendered inoperative, since so long as any one of the thermostats isintermediately positioned in response to an approximately normaltemperature, the resistances of that thermostat will still be effectiveto control the two thermostat circuits and to vary the position of thebalanced solenoid H9. This combination of the thermostatic members willcontrol the heating system in response to an average of the temperaturesexisting at the locations of the several thermostats, even though two ofthe thermostats may be temporarily subject to opposite extreme orabnormal temperatures.

'I'he limiting conditions as to the number of thermostats which can beconnected in series as shown in Fig. 4 will be determined by the sum ofthe resistances reaching such a value that the current flowing in thebalanced solenoid |49, and hence the flux produced. is so reduced as tobe insulllcient to cause proper operation of the f switch |53. If it isdesirable to use more thermostats than this number, a plurality ofhook-ups similar to that shown at the left of Fig. 4 can be connected inparallel across the lines I l5, IIB and IH. For example, a second seriesof wires II5, H6' and H1' are shown in Fig. 4 traveling from the wiresII5, HG and Ill, respectively. These branch wires will extend to asecond group of three thermostats similar to L, L' and L", and similarlyconnected. With such an installation the heating system will becontrolled in accordance with an average of the average temperaturesrecorded by each of the two groups of thermostats. In practice it hasbeen found convenient to use 9, 16 or 25 thermostats for largeinstallations. If nine are used, there will be three groups of threethermostats each, the groups being connected in parallel with thesolenoid |49, and the thermostats in each group being connected in themanner shown in Fig. 4 for thermostats L, L and L". If sixteenthermostats are used, there will be four groups of four thermostatseach, and if twenty-five are used there will be ve groups of fivethermostats each. For such groupings a single standard type ofthermostat of fixed resistance can be used and maintain approximatelythe desired total resistance in the control circuit. However, bysuitably varying the resistance in the thermostats, the number of groupsand the number of thermostats in each group may be chosen as found to bedesirable or necessary.

Referring now briefly to the general operation of this heating system,the production of steam at the generator A will be so regulated as tosupply steam at substantially the proper sub-atmospheric pressure toreplace the heat loss from the building. The pressure operatedcontroller C will respond to variations in the pressure differentialbetween the supply and return sides of the system so as to maintain theradiators D filled (or partially filled in very mild weather) with steamat a pressure approximately suilicient to replace these heat losses. Incase the average temperature produced within the building by means ofthis heating system exceeds the predetermined desired temperature, theseveral thermostats L, L' and L" will cooperate to cause theelectrically operated mechanism K to partially close the valve C and cutdown the flow of steam to the radiators. The valve C will still be underthe control of the differential-pressure operating mechanism, but themaximum opening of the valve C will be limited by the position ofcontrol lever 99 which is determined by the action of the thermostaticmechanism. In case the average temperature within the building fallsbelow the desired standard. lever 99 will be automatically adjusted soas to permit a wider opening of the control valve C, and this opening ofthe valve will be effected by the differential pressure mechanism atsuch a rate as to maintain the proper efficient supply of steam to theradiators.

We claim:

1. In a temperature control device. the combination of a plurality ofcontrol devices each comprising a thermostat, a pair of resistances, apair of movable contact members one engaging each of the resistances,and means actuated by the thermostat for simultaneously moving thecontacts lengthwise of the resistances, a pair of control circuits, th'eeffective portions oi all of one set of similar resistances of theseveral control devices being connected in one circuit, and theeffective portions of the other set of resistances being connected inthe other circuit, and controlling mechanism governed by the controlcircuits.

2. In a temperature controlling mechanism, the combination of aplurality of control devices each comprising a thermostat, a pair ofresistances, a pair of movable contact members one engaging eachresistance, and means actuated by the thermostat for simultaneouslymoving the contacts lengthwise of the respective resistances, athree-wire controlling circuit in which the control devices areconnected so that the eiective portions of the similar resistances ofall of the control devices are connected in series between theintermediate wire and one side wire of the three-wire circuit, and theeffective portions of the other set of resistances are connected inseries in the other side of the three-wire circuit, and a controllingmechanism operable by the circuit.

3. In a temperature controlling mechanism, the combination of aplurality of control devices cach comprising a thermostat, a pair ofresistances. a pair of movable contact members one engaging eachresistance. and means actuated by the thermostat for simultaneouslymoving the contacts lengthwise of the respective resistances, athreewire controlling circuit, the intermediate wirc being connected tothe two movable contacts of the control devices at one end of theseries, wires connecting the respective ends of the resistances of thisrst control device to the respective movable contacts engaging thecorresponding resistances of the next device of the series, similarwires connecting these latter resistances with the movable contacts ofthe next device and so on throughout the series, the two outside wiresci" the controlling circuit being connected to the respective ends ofthe two resistances of the last device in the series, whereby theeffective portions of one set of the resistances of all of the controldevices are connected in series in one side of the controlling circuit,and the effective portions of the other set of resistances are connectedin series in the other side of the controlling circuit. and acontrolling mechanism operable by the controlling circuit.

4. Temperature controlling means for a steam heating system comprising asteam supply valve, means for controlling the setting of the valve inaccordance with pressure changes at the low pressure side of the valve,and means for thermostatically controlling the valve in accordance withthe average of the temperatures existing at a plurality of locationscomprising a motor device for adjusting the valve an amountproportionate to the variation from a predetermined temperature, a pairof control circuits for the motor, one for determining movement in onedirection and the other in the other direction, a plurality oftemperature control devices each comprising a thermostat, a pair ofsimilar resistances for each thermostat, a contact engaging with eachresistance, and means operable by the thermostat for simultaneouslymoving the contacts lengthwise of the resistances, and connectionswhereby the effective portions of the i similar resistances of all oithe control devices are connected in series in one control circuit, andthe effective portions of the other set of resistances are connected inseries in the other circuit. Y

5. Temperature controlling means for a steam heating system comprising asteam supply valve, means for controlling the setting of the valve inaccordance with pressure changes at the low pressure side of the valve,and means for thermostatically controlling the valve in accordance withthe average of the temperatures existing at a plurality of locationscomprising a motor device for adjusting the valve an amountproportionate to the variations from a predetermined temperature, athree-wire control circuit for the motor, a plurality of temperaturecontrol devices each comprising a thermostat, a pair of similarresistances for each thermostat, a contact engaging with eachresistance, and means operable by the thermostat forsimultaneouslymoving the contacts lengthwise of the resistances, andconnections whereby the effective portions of the similar resistances ofall of the control devices are connected in series between theintermediate Wire and one side wire of the three-wire circuit, and theeiective portions o! the other set of resistances are connected inseries in the other side of the circuit.

6. Temperature controlling means for a steam heating system comprising asteam supply valve, pressure-operated means for controlling the settingof the valve in response to pressure changes at the low pressure side ofthe valve, and thermostatically controlled means for restricting theopening of the Valve by the pressure-operated means in proportion tovariations from a predetermined average of the temperatures at aplurality of locations, said means comprising a motor device foradjusting the valve an amount proportionate to the variation from thepredetermined average temperature, a plurality of temperature controldevices each comprising a thermostat, a pair of similar resistances foreach thermostat, a contact engaging with each resistance, means operableby the thermostat for simultaneously moving the contacts lengthwise ofthe resistances, a pair oi control circuits for the motor, andconnections whereby the effective portions of the similar resistances ofall ot the control devices are connected in series in one circuit, andthe effective portions oi.' the other set oi resistances are connectedin series in the other circuit.

7. Temperature controlling means for a steam heating system comprising asteam supply valve, pressure-operated means for controlling the settingof the valve in response to pressure changes at the low pressure side otthe valve, and thermostatically controlled means for restricting theopening of the valve by the pressure-operated means in proportion tovariations from a predetermined average oi' the temperatures at aplurality of locations, said means comprising a motor device foradjusting the valve an amount proportionate to the variation from thepredetermined average temperature, a plurality of temperature controldevices each comprising a thermostat, a pair of similar resistances foreach thermostat, a contact engaging with each resistance, means operableby the thermostat for simultaneously moving the contacts lengthwise ofthe resistances, a three-wire control circuit for the motor, andconnections whereby the eiiective portions of the similar resistances ofall of the control devices are connected in series between theintermediate wire and one side wire of the circuit, and the effectiveportions ci the other set of resistances are connected in series in theother side of the circuit.

8. In a temperature control device for a steam heating system, thecombination of a plurality of control devices each comprising athermostat and a variable resistance controlled by the thermostat, amotor means and a control circuit for the motor means including theeffective resistances of the several control devices, the controldevices being divided in groups, the effective resistances of each groupbeing connected in series, and the several groups being connected inparallel in the control circuit.

9. In a temperature control device for a steam heating system, thecombination of a plurality oi control devices each comprising athermostat, a pair of resistances, a pair of movable contact members oneengaging each of the resistances and means actuated by the thermostatfor simultaneously moving the contacts to vary the effective portions ofthe resistances, a valve controlling mechanism, a. pair of similarcontrol circuits for the valve controlling mechanism, the controldevices being divided into groups, each oi the control circuits beingdivided into several parallel branch control circuits. one for eachgroup, the eiective portions of all of one set of similar resistances ofthe several control devices in anyone group being connected in onebranch circuit for that group and the effective portions of the otherset of resistances being connected in the other branch circuit for thatgroup.

10. In temperature regulating mechanism the combination of a motorhaving two controlling circuits; a plurality o! msistances connected inseries for each circuit; a plurality of thermostats; and meansassociated with each thermostat for simultaneously cutting resistanceinto one of the circuits and cutting resistance out oi' l the othercircuit.

11. 1n temperature regulating mechanism for steam heating systems. thecombination of a. steam supply valve; pressure responsive means forcontrolling the valve; and temperature responsive means for controllingthe valve comprising a motor having two controlling circuits, aplurality of resistances connected in series for each circuit, aplurality of thermostats, and means associated with each thermostat forsimultaneously cutting resistance into one of the circuits and cuttingresistance out of the other circuit.

ELBERT A. TAYLOR. MILLARD D. FENCE. CLAYTON A. DUNHAM.

DISCLAIMER Re. 20,3NL`EZber't A. Tag/lor, Arlingtun Heights, Ill.,j'il/lmv/ l). Pfmvf, Nvw York,

N. Y., and (ayfm A. [lun/mm. (`rlm1(00, Ill. Avlcnxm: 'VMMi icn.\'rll i:(Wm- TROL MECHANISM FOR HEATING SYSTEMS. Intint Iamd Marrll 23S, |937.Disclaimer filed N'Inrcll 24, 1.035%, by Lim ussigmo` 11. [hm/mm(hm/muy. Newby unters this disclaimer to 'lnim l() of Suid rvissllwlpatent.

[f'a/ (azwltr) April If), [93H]

